1. Variation: one variable changes, and the other variable also changes.

2. Positive proportion: refers to two related quantities, one of which changes and the other changes. If their ratio is certain (that is, the quotient is certain), then they are in direct proportion.

Example: A÷B=K (certain) division relation; A=K (certain) b

3. Judge the proportional relationship

Two related quantities, one of which changes with the other (simultaneously expands or contracts);

When their proportions are constant, they are in direct proportion, and the image of direct proportion is: a straight line.

4. Inverse ratio

Meaning: two related quantities, one of which changes and the other changes accordingly. If the product of the corresponding two numbers in these two quantities is certain, these two quantities are called inverse ratio.

5 the judgment method of inverse proportion

Two related quantities, one quantity changes and the other quantity changes (one quantity increases and the other quantity decreases). When their products are unchanged, the opposite products must be inversely proportional;

The inverse scale image is: a curve.

6. Scale

Scale: The ratio of the distance on the map to the actual distance is called the scale of this map. Distance on the map ÷ actual distance = scale (note: unit).

Distance on the map ÷ scale = actual distance; Actual distance × scale = distance on the map.

7. Scale classification

Line segment scale; Digital scale.